1. Field of the Invention
The present invention relates to a printing apparatus and a printing method, and relates in particular to a printing apparatus for high-speed paper supply and a printing method therefor.
2. Related Background Art
In a conventional apparatus, in order to increase printing speeds and to simplify mechanisms, a paper feeding mechanism, a paper conveying mechanism and a carriage mechanism are independently driven, or special motors are provided to drive these mechanisms at optimal timings.
However, the following problem plagues a conventional system, comprising these mechanisms, that initiates the feeding of a succeding printing medium without detecting the trailing end of a preceding printing medium. For example, when the lengths of printing media differ between a predecessor and a successor or when the lengths of the printing media vary, or when slippage occurs at a paper feeding mechanism, preceding and succeding media overlap each other, so that in a printing apparatus that has only one paper sensor a trailing edge of the preceding printing medium and a leading edge of the succeeding one cannot be discriminated, thereby causing paper feeding failures.
If the trailing end of the preceding printing medium is detected first and then the feeding of the succeeding printing medium is started, the above problem can be avoided. However, unless the sensor for the printing medium is located very near the feeding mechanism, a satisfactory effect can not be obtained because the interval between the preceding and succeeding printing media will be extended. Further, in the printing apparatus, the leading edges of printing media are detected immediately after the media are fed by a feeding mechanism, so that, if because of slippage the feeding distance of the printing media varies before they reach the sub-scanning mechanism, there is no means available to correct such variation. Therefore, no conventional printing apparatuses can cope with reductions in the intervals between printing media that are consecutively fed, stabilization in positioning the leading edges, and differences in the lengths of printing media. For removing the above-mentioned trouble, it is generally effective to employ two paper sensors, but such a use results in increased manufacturing costs.
It is, therefore, one objective of the present invention to provide a printing apparatus that enables fast printing, by increasing the speed of the paper feeding operation, and a printing method therefor.
To achieve the above objective, according to one aspect of the invention, a printing apparatus for printing on a printing medium employing a printing head, comprises:
feeding means for feeding a printing medium toward the printing head;
detection means for detecting an edge of the printing medium fed by the feeding means; and
control means for controlling the driving of the feeding means so as to (1) cause the feeding means to initiate the feeding of a succeeding printing medium after the feeding means initiates the feeding of a preceding printing medium and before the detection means detects a trailing edge of the preceding printing medium and (2) cause a leading edge of the succeeding printing medium to arrive at the detection means after the detection means detects the trailing edge of the preceding printing medium.
Further, according to another aspect of the invention, a printing method for printing on a printing medium with a printing head, comprises the steps of:
feeding a printing medium toward the printing head;
initiating the feeding of a succeeding printing medium toward the printing head, after the feeding of a preceding printing medium is initiated and before a trailing edge of the preceding printing medium is detected at a predetermined position; and
feeding the succeeding printing medium so that a leading edge of the preceding printing medium arrives at the predetermined position after the leading edge of the preceding printing medium is detected at the predetermined position.
In this specification, xe2x80x9cprintingxe2x80x9d includes not only the formation of meaningful information, such as characters or figures, on a printing medium, but also includes the formation of various images, designs and patterns on a printing medium or the processing employed for the printing medium, whether or not they convey any meanings or whether or not they can be visually distinguished by humans.
The term xe2x80x9cprinting mediumxe2x80x9d refers not only to a paper that is used by a common printing apparatus, but also to various other types of media, such as cloth, plastic film and metal plates, that can accept ink.
Further, xe2x80x9cinkxe2x80x9d should be appreciated broadly as the definition of xe2x80x9cprintingxe2x80x9d. That is, it should be understood as liquid that can be applied onto a printing medium to form images, designs and patterns, or liquid that can be used to process the printing medium.